I'd like to know what those fans are that they use in conjunction with a parachute to fly around and if you need some kind of certification to fly them.

Thanks!

No certification neccasary. It is called a ''powered paraglider''. Wiki link:
http://en.wikipedia.org/wiki/Powered_paraglider

The part on your back is called a paramotor.

power paraglider or a jetpack

To answer your question correctly they are a 2-cycle engine with direct drive to a 30-inch propeller (pusher propeller). These are used on paragliders, which operate under Title 49 U.S. Code Part 103.

para motor